Fix flake.nix to use correct uv2nix API

Use editablePythonSet with mkVirtualEnv and add proper UV environment variables.

Author: kfl

flake.nix

@@ -43,15 +43,27 @@
           };
 
           # Create Python set with overlay applied
-          python = pkgs.python314.override {
+          pythonSet = (pkgs.python314.override {
+            self = pythonSet;
             packageOverrides = lib.composeManyExtensions [
               pyproject-build-systems.overlays.default
               overlay
             ];
+          });
+
+          # Create editable overlay for development
+          editableOverlay = workspace.mkEditablePyprojectOverlay {
+            root = "$REPO_ROOT";
+          };
+
+          # Apply editable overlay
+          editablePythonSet = pythonSet.override {
+            self = editablePythonSet;
+            packageOverrides = editableOverlay;
           };
 
-          # Create virtual environment with editablePackages
-          venv = python.pkgs.mkVirtualEnv "staffeli-nt-env" workspace.deps.default;
+          # Create virtual environment with all dependencies
+          venv = editablePythonSet.mkVirtualEnv "staffeli-nt-dev-env" workspace.deps.all;
 
         in
         {
@@ -61,7 +73,16 @@
               pkgs.uv
             ];
 
+            env = {
+              UV_NO_SYNC = "1";
+              UV_PYTHON = editablePythonSet.python.interpreter;
+              UV_PYTHON_DOWNLOADS = "never";
+            };
+
             shellHook = ''
+              unset PYTHONPATH
+              export REPO_ROOT=$(git rev-parse --show-toplevel)
+
               echo "Staffeli NT development environment"
               echo "Python: $(python --version)"
               echo ""